Circuit for periodically generating oscillations



Sept. 7, 1948. E JQR. 'MC DORE 2,448,543

CIRCUIT FOR PERIODICALLY GENERATING OSCILLATIONS I Filed Nov. 28, 1942 OUTPUT SQUARE WAVE GENERATOR FIG. 2.

FIG. 3.

FIG. 4.

' INVENTOR JAMES R. MOORE meof any royalty thereon.

description; thereof progresses.

Patented Sept. 7, 1948 32.:

momma H 2,4d8 ,543 r, V V mmmems easements.

OSCILLATIONS I James lit Moore, Rumson, N. J., assignor to the United States of Ame A the Secretary of War rice 'asrepresented by Y Applicationhl'oveinber 23, 1942, Serial to. 4 7,271

401mm. florzsof-sel hemmed under the act 01 March 3, 1883, as

'amendedApril 30,1928; 370 o. o. 757) r The invention described herein may bemanuf-actured and'used by or for the Government for governmental purposes, without thepayment to My present invention'relates to electronic circults and more particularly to circuits for periodic'ally generating electrical oscillations of con- 'stant-or varying amplitude.

It is the main'obiect of my present invention toprovide means of the general character indicated which enables-the substantially instantaneous production of electrical oscillations and i also the substantially"instantaneous cessation of such oscillations. a r 1 It'is thef urther pbjectof my presentinvention to provide a circuit whereby the amplitude of the oscillations produced can be maintained at a constant level or can be made to increase or decrease in a'given time interval at the will of the operator. i

The oscillations produced by means of the present invention are of particular value in the production of an accurate calibrating w ave such as is described in my copending applicationiencopending applications entitled Method and means for determining, range," Serial Number 467,26l,'a1so filed of even .datefherewith."

Other objects and advantages of the, present invention will readilyoccur to those skilled in the art to which-the same relates as the detailed In the accompanying drawings,

Figure 1 is a schematic diagram of an "scillating circuit assembled in accordance with the principles of the present invention;

Figure 2 is an osc llogram of a damped sine wave such as is normally produced by a shock any appropriate generator, I prefer that it comprise a portion of the output of a. keyer'constitilting a component of a pulse-.echo-system for target detection. The frequency of this voltage will depend, in. a well known manner, upon the maximum effectiverange of the particular target detecting system. i p.

The square wave thus obtained is applied to the control grid of a trigger tube T1. Such tube preferably comprises a tetrodeyin which the potentiometer 5 to. the negative terminal of a source 6ofd.'-c. voltage, the control grid is '5 biasednegatively through the adjustable contact arm I of the potentiometer, the screen grid is connected through a resistance 8 to the positive terminal ofthe source 870i d.-c.- voltage, and the plate is directly connected to said source of d.-c.

voltage. By reason of the character or the voltagefed to the tube Tr said tube becomes alter- Connected between the cathode ofithe tube Ti and the positive side of the source 610i d.-c. voltage, at a point 9, which is at a lower potential than is connected to the plate of said tube.

'is'a tank circuit 10 comprising the parallel inductance' L and capacitance C, the resonant'fre- "'quency of the tank circuit being a multiple, not necessarily integral, of the frequency of the square Wave voltage applied to the grid of the tube T1. This arrangement is such that when the tube T1 is conducting it shunts the tank circuit instantaneously: ceases to oscillate, whereas, as

a "said tubebecomes non-conducting. the tank circult is sho'ckexcited and substantially instan taneously commences to oscillate.

These oscillations, shown in Figure 2 of the drawings, are normally damped and if it is desired to maintain the amplitude at a constant level, it is necessary to provide a means to make up for the losses in the tank circuit.

For this purpose, I provide a vacuum tube oscillator, preferably having a negative resistance characteristic such as is shown on page 1221 of Proceedings I. R. E., volume 23, 1935. The normal output of such an oscillator is a sine wave of gradually increasing amplitude as shown in Figure 3 of the drawings.

This oscillator preferably comprises a pentode tube T2 the screen grid of which is directly receptive of the oscillating output of the tank circuit l0 and the suppressor grid of which is also receptive of said output through the capacitance 3 I I. The cathode of this tube is connected to the negative terminal of the source .6 of d.-c. voltage and the control grid may, if desired, be biased negatively with respect to the cathode by .any well :known means. The tube obtains its negative resistance characteristic by reason of its plate being connected at the point l3 on the source 6 of d.-c. voltage which is at a lower potential than the point 9 to-which the screen g rid is connected through the tank circuit t0, and-by reason of its suppressor grid. being; biased negatively with respect to its cathode'throug'hthe.

bias battery I2 and resistance 12'. The output of the oscillator is obtained througha conductor l4 connected into the screen grid circuit. P

It is to be noted that the outputof. the tank circuit l and the output of the oscillator tube the -output thereof at predetermined amplitude T2 are in phase and if tlieamplitudeef the' for m-er" decreases at the same rate as the amplitude of the latter increases, combining both results in a constant amplitude sine wave, such as is shown in Figure 4 of the. drawings; Itfollows-that by altering the resistance of the tank circuit or the oscillating vacuum tube circuit the rate of damping-of the former or building up of the latter can be varied and any-desired variations in the amplitude level of the combined waves can thus be :obtained.

A constant amplitude sine Wave obtained as above is particularly useful for controllin the generationlof a calibrating'wave of; square configuration and for this purpose, the circuit herein shown and described may be readily substituted for the oscillation producing portion of the time wave generatingcircuit described in my. copending application first above'identified.

It will be noted :from all-of the :foregoing that levels during the oscillating periods.

'3. Apparatus for producing electrical oscillations comprising, a resonant circuit, an alternately conducting and non-conducting electronic circuit for periodically shunting said resonant circuit with a variable impedance whereby said resonant circuit is caused alternately to oscillate and to cease oscillating, and an electronic circuit having a negative resistance characteristic coupled to said resonant circuit for maintaining the out- I have provided a circuit :for the periodic generation .of very stable .sine wave oscillations, the commencement and cessation of said oscillations being-substantially instantaneous and the am- .plitudethereof being constant or variable at will.

While. I have set. forth :a preferred form .of my invention it is.:to .be clearly :understood that I do inotwish to. .be, limited to the-exact details or the specific, application iherein shown and described ifor purpose of illustration only, inasmuch as :tions comprising, .a resonant circuit, means for periodically. shunting said resonant circuit. with .a variable impedance whereby said resonant cir cuit; isicaused alternately rto .oscillateand to cease oscillating, and an electronic circuitihaving a negput thereof at predetermined amplitude levels durin the oscillating periods.

4, Apparatus for producing electrical oscillations comprising, aresonant circu iiran alternately conducting and non-conducting electronic circuit for alternately exciting said resonant {circuit and shunting the same with .a low impedance whereby said resonant circuitis caused alternate- .ly to oscillate and :to cease: oscillating, and an electronic circuit having a n gative resistance characteristic coupled to said resonant circuit for maintaining the output thereof at predetermined amplitude levels during the oscillating periods.

JAMES-R MOORE.

REFERENCES. CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,773,556 Von Arco Aug. 19, 1930 1,908,249. Hund May;9, 1933 2,029,488 Koch 4 Feb. 4, .1936 2,092,098 Turner :Sept. .7, 1937 2,130,272 Ford Sept. 13, 1938 2,244,003 Eaglesfield June.3, 1941 2,274,347 Rust Feb-24, 1942 2,364,756 Roberts Dec. 12, 1944 2,370,685 Rea Mar. '6, 1945 OTHER REFERENCES Pro. I. R. E,, vol. .27, No. 2, February 1939, pages 88-94. 

